Solid-liquid separation system

ABSTRACT

Methods and apparatus for separating liquid products and catalyst fines from a slurry used in a Fischer-Tropsch reactor. A settling system continuously or intermittently removes catalyst fines from the slurry and is coupled with catalyst-liquid separation system that separates liquid products from the slurry. The preferred separation system produces a sub-particle rich stream and a catalyst-lean stream that are removed from the system. The systems of the present invention act to reduce the concentration of catalyst fines in the reactor, thereby increasing the effectiveness of a catalyst-liquid separation system.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] The present invention relates generally to methods and apparatusfor separating liquid products from a slurry comprising solid particlesand liquids. More specifically, the present invention relates to methodsand apparatus for separating liquid products from a slurry used in aFischer-Tropsch slurry bubble column reactor.

[0004] A Fischer-Tropsch reaction generally entails contacting a streamof synthesis gas (hydrogen and carbon monoxide) with a catalyst undertemperature and pressure conditions that allow the synthesis gas toreact and form hydrocarbons. More specifically, the Fischer-Tropschreaction is the catalytic hydrogenation of carbon monoxide to produceany of a variety of products ranging from methane to higher alkanes,olefins, and oxygenated hydrocarbons or oxygenates. Research continueson the development of more efficient Fischer-Tropsch catalyst systemsand reaction systems that increase the selectivity for high-valuehydrocarbons in the Fischer-Tropsch product stream.

[0005] Originally, the Fischer-Tropsch synthesis was operated in fixedbed reactors. These reactors have several drawbacks, such as temperaturecontrol, that can be overcome by gas-agitated slurry reactors or slurrybubble column reactors. Gas-agitated reactors, sometimes called “slurryreactors” or “slurry bubble columns,” operate by suspending catalyticparticles in liquid and feeding gas reactants into the bottom of thereactor through a gas distributor, which produces small gas bubbles. Asthe gas bubbles rise through the reactor, the reactants are absorbedinto the liquid and diffuse to the catalyst where, depending on thecatalyst system, they are converted to gaseous and liquid products. Asgaseous products are formed, they enter the gas bubbles and arecollected at the top of the reactor.

[0006] Because of the formation of liquid products (commonly calledwaxes in this context), it is necessary to maintain the slurry at aconstant level by continuously or intermittently removing liquidproducts from the reactor. One problem with the removal of liquids,however, is that catalyst particles are dispersed in the liquid and mustbe separated from the slurry and, in some cases, returned to the reactorin order to maintain a constant inventory of catalyst in the reactor.Several means have been proposed for separating the catalyst from theliquid products, e.g., centrifuges, sintered metal filters, cross-flowfilters, magnetic separators, gravitational settling, etc.

[0007] Filtration is one of the catalyst-liquid separation methods usedwith Fischer-Tropsch reactors. Filtration techniques are characterizedby solid-liquid separation systems that remove liquid products from aslurry by drawing the fluid across a filter medium. The filter mediummay be simply a filter substrate or may be composed of a filter cakedisposed on a filter substrate, such that the filter cake forms aprimary filter. A filter cake is formed as solid particles are depositedon the filter substrate creating a permeable barrier between the slurryand the substrate. The thickness and permeability of the filter cake iscritical to the efficient operation of the filtration system.

[0008] In a commercial slurry bubble column reactor, the severehydrodynamic conditions inside the reactor, coupled with the desiredlong lifetime of the catalytic material, typically results in catalystattrition. As the catalyst breaks down over time, sub-particles ofvarious sizes may be created, including very small particles known as“fines,” some of which may even be sub-micron in size. The presence offines in the reactor tends to greatly reduce the effectiveness of thecatalyst-liquid separation system.

[0009] In a catalyst-liquid separation system utilizing filtration,cycle time between backwashing operations, as well as filter life, maybe greatly reduced because the fines tend to reduce the permeability andflux of the filter system. Likewise, centrifuges and gravitationalsettlers have been found unsuccessful in reducing the percentage offines because the fine particles are so small that they will not settleout of the liquid solution in a practical amount of time, if at all.Magnetic separation has been similarly ineffective in removing catalystfines from the slurry. Thus the performance of a catalyst-liquidseparation system has hereto been undesirably dependent upon the age ofthe catalyst. For example, when the catalyst is new the catalyst-liquidseparation system operates at a very high rate that decreases as thecatalyst breaks down.

[0010] Thus, there remains a need in the art for methods and apparatusto maintain the effectiveness of a catalyst-liquid separation systemindependent of the age or degree of attrition of the catalyst.Therefore, the embodiments of the present invention are directed tomethods and apparatus for removing catalyst fines from a slurry thatseek to overcome the limitations of the prior art.

SUMMARY OF THE PREFERRED EMBODIMENTS

[0011] Accordingly, there are provided herein methods and apparatus forseparating liquid products and catalyst fines from a slurry used in aFischer-Tropsch reactor. The preferred embodiments of the presentinvention are characterized by a settling system that continuously orintermittently removes catalyst sub-particles fines from the slurry byway of a sub-particle rich stream, coupled with a distinct separationsystem that separates the slurry into a catalyst-rich stream and acatalyst-lean stream that supplies most of the commercial products ofthe reactor system. The embodiments of the present invention act toreduce the overall concentration of catalyst fines in the slurry,thereby increasing the effectiveness and/or the life of acatalyst-liquid separation system.

[0012] One preferred embodiment includes a slurry bubble column reactorsystem having a first circulation loop with a catalyst-liquid separationsystem that separates the slurry into a catalyst-rich stream and acatalyst-lean stream. The catalyst-lean stream provides a stream fromwhich most of the products of the reactor can be extracted. In thisembodiment, the reactor system also includes a second circulation loopthat, in some preferred embodiments, comprises a settling chamber, whichsegregates at least a portion of catalyst sub-particles from catalystparticles. A sub-particle lean stream and a sub-particle rich stream canthen be extracted from the settling chamber. The sub-particle richstream, which may contain a portion of the liquid products, can then beremoved from the system, and may be further processed if desired torecover some of the liquid products. It will be understood that theterms “rich” and “lean” are relative terms, so that, for example,“sub-particle rich stream” refers to a stream containing a higherproportion of sub-particles, as compared to other particles, than otherstreams in the system. The overall concentration of catalyst fines inthe slurry is maintained at a reduced level, thereby increasing theeffectiveness and life of the catalyst-liquid separation system.

[0013] In a second preferred embodiment, a slurry bubble column reactorsystem has only one circulation loop, which includes both a settlingchamber and a catalyst-liquid separation system. The slurry movesthrough the settling chamber, from which is extracted a sub-particlerich stream that is removed from the system. The sub-particle leanstream can then be processed in the catalyst-wax separation system toproduce a catalyst-rich stream and a catalyst-lean stream. Productionquantities of liquid products can then be collected from thecatalyst-lean stream. In addition, some liquid products can be recoveredfrom the sub-particle rich stream after further processing.

[0014] The present invention may also be embodied as a method forremoving solids from a slurry by circulating the slurry through asettling chamber to produce a sub-particle lean stream and circulatingthe slurry through a catalyst-liquid separation system to produce acatalyst-lean stream. The preferred embodiment may also include removingthe sub-particle lean stream and the catalyst-lean stream from thesystem.

[0015] Thus, the present invention comprises a combination of featuresand advantages that enable it to substantially reduce the concentrationof catalyst fines in the slurry, thereby increasing filter effectivenessand life. These and various other characteristics and advantages of thepresent invention will be readily apparent to those skilled in the artupon reading the following detailed description of the preferredembodiments of the invention and by referring to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For a more detailed understanding of the preferred embodiments,reference is made to the accompanying Figures, wherein:

[0017]FIG. 1 is one embodiment of a slurry bubble column reactor systemhaving two circulation loops;

[0018]FIG. 2 is a graph depicting the size distribution of an unusedcatalyst system;

[0019]FIG. 3 is a graph depicting the size distribution of a usedcatalyst system;

[0020]FIG. 4 is a graph illustrating the expected performance curves ofa filter operating with and without removal of fines;

[0021]FIG. 5 is a detailed view of one embodiment of a preferredsettling system; and

[0022]FIG. 6 is one embodiment of a slurry bubble column reactor havinga single circulation loop.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the description that follows, like parts are marked throughoutthe specification and drawings with the same reference numerals,respectively. The figures are not necessarily to scale. Certain featuresof the invention may be shown exaggerated in scale or in somewhatschematic form and some details of conventional elements may not beshown in the interest of clarity and conciseness.

[0024] The preferred embodiments of the present invention relate tomethods and apparatus for effectively removing liquid products from aslurry containing solid catalyst particles, at least a portion of whichare very small catalyst sub-particles, or fines, formed by catalystattrition. The present invention is susceptible to embodiments ofdifferent forms. There are shown in the drawings, and herein will bedescribed in detail, specific embodiments of the present invention withthe understanding that the present disclosure is to be considered anexemplification of the principles of the invention, and is not intendedto limit the invention to that illustrated and described herein.

[0025] In particular, various embodiments of the present inventionprovide a number of different methods and apparatus for removing liquidproducts from a slurry. The concepts of the invention are discussed inthe context of a Fischer-Tropsch slurry bubble column reactor but, useof the concepts of the present invention is not limited to slurry bubblecolumn reactors or to the Fischer-Tropsch process in general and mayfind use in any reacting or non-reacting fluid-solid system, or anyfiltering or separating application. It is to be fully recognized thatthe different teachings of the embodiments discussed below may beemployed separately or in any suitable combination to produce thedesired results. In the context of the current description, the slurryis defined as a liquid that contains solid particles of anyconcentration. The slurry should not be read as indicating a specificconcentration of solid particles within the fluid. It should also beunderstood that the concentration of solid particles within the slurrywill change, depending on the location of the slurry within the reactorassembly.

[0026] As used herein, reactor slurry is defined as the composition ofcatalyst particles and hydrocarbon liquids generally found in thereactor. It is understood that the exact composition of the reactorslurry within the reactor may not be constant throughout the reactor andthat the exact composition of the reactor slurry is not critical to theoperation of the separation techniques discussed herein.

[0027] In the current context, the sub-particle rich stream is definedas a stream of slurry that has had a portion of the larger catalystparticles removed. Therefore, among the catalyst in the sub-particlerich stream, there is a higher concentration of catalyst sub-particlesas compared to the composition of catalyst in the reactor slurry. Asub-particle lean stream is defined as a stream of slurry from whichsome catalyst sub-particles have been removed. Therefore, among thecatalyst in the sub-particle lean stream, there is a lower concentrationof catalyst sub-particles as compared to the composition of catalyst inthe reactor slurry.

[0028] A catalyst-lean stream is defined as a stream of slurry fromwhich the majority of the catalyst particles have been removed. Thecatalyst-lean stream has a lower concentration of catalyst particlesthan the reactor slurry and is preferably substantially free of catalystparticles in order to be suitable for further processing into commercialproducts. A catalyst-rich stream is defined as a stream of slurry fromwhich a portion of the liquid hydrocarbons has been removed. Thecatalyst-rich stream therefore has a higher concentration of catalystparticles than the reactor slurry.

[0029] Referring now to FIG. 1, a slurry bubble column reactor system100 includes a slurry reactor 110, a settling system 220, and acatalyst-liquid separation system 250. Reactor 110 includes a reactorchamber 120 containing a catalyst 180 suspended in a slurry. Settlingsystem 220 includes settling chamber 280, lines 230 and 235 connectingthe settling chamber to reactor 110, sub-particle rich stream outlet210, and gas outlet 240. Optionally, a degasser vessel (not shown) mayremove gas from the slurry before it enters chamber 280. Settling system220 may also include an internal plate 245, or other internal structure,for improving the settling characteristics of chamber 280.Catalyst-liquid separation system 250 includes a separation unit 290connected to reactor 110 by lines 260 and 270. Separation system 250also includes outlet 205 for the catalyst-lean stream to providesubstantially solids-free hydrocarbon products. Optionally, a degasservessel (not shown) may remove gas from the slurry before it entersseparation unit 290.

[0030] A feed gas is supplied through line 115 into reactor 110 that isfilled with a reactor slurry. Product gases flow through gas outlet 125while liquid products combine with the reactor slurry. Reactor slurrypasses into settling system 220 via line 235 and into catalyst-liquidseparation system 250 via line 260. Catalyst-liquid separation system250 produces a catalyst-lean stream through outlet line 205 and recyclesa catalyst-rich stream to reactor 110 through line 270. Settling system220 produces a sub-particle rich stream through outlet 210 and asub-particle lean stream, which is recycled to reactor 110 through line230. A preferred settling system 220 also provides an outlet for gasthrough outlet 240. Gas outlet 125 from reactor 110 and gas outlet 240from settling system 220 can be combined into one single gas outlet, asshown in FIG. 1, but it should be understood that they do notnecessarily need to be combined. It is also understood that any gasoutlet from any optional degasser (not shown) also could be combined ornot with any of the two gas outlets 125 and 240. Settling system 220 andcatalyst-liquid separation system 250 create two distinct flow loopsthat circulate slurry.

[0031] Slurry bubble column reactors, such as reactor 110 shown in FIG.1, function by bubbling gas through inlet 115 into a reactor slurry inwhich are suspended particles comprising a catalyst 180. As the gasbubbles rise through the reactor, the reactants are absorbed into thereactor slurry and diffuse to the catalyst where, depending on thecatalyst system, they are converted to gaseous and liquid products. Gasproducts exit the top of reactor 110 through gas outlet line 125 whileliquid products mix with the reactor slurry. One exemplary slurry bubblecolumn reactor is described in co-owned U.S. patent application Ser. No.10/023,258, titled “Slurry Bed Reactor With Well-Mixed Gas Flow Regime,”which is incorporated herein by reference for all purposes.

[0032] Therefore, the liquid products must continuously be removed fromthe reactor slurry in order to maintain the total volume of liquidscontained in the reactor. The effectiveness of the catalyst-liquidseparation may also be dependent on the size of the catalyst particlesfound in the circulating slurry. In a given reactor slurry, catalystparticles ranging in diameter from less than 1 micron to as much as tensof microns may be present. FIG. 2 shows a model size distribution for anewly fabricated catalyst. As the reactor operates, the catalystparticles are subjected to extreme hydrodynamic conditions that will,over time, tend to break down the catalyst into increasingly smallerparticles. As shown in FIG. 3, after being used for a period of time,the distribution of particle size will change to include an increasingnumber of very small particles, as indicated at 410. It is these verysmall catalyst sub-particles (fines) that not only decrease theeffectiveness of the catalyst-liquid separation system but may haveother detrimental effects on the system as a whole.

[0033] As previously discussed, the liquid products produced by thereaction are separated from the reactor slurry in a catalyst-liquidseparation unit. One of the preferred types of separation units usesfiltration to separate the solid catalyst particles from the liquidproducts. Although filtration has proven to be very effective inproviding a clean liquid product, filters are also susceptible to a lossof permeability or flux, especially in the presence of a highconcentration of solids, in particular catalyst fines. The dashed lineof FIG. 4 illustrates the filtration effectiveness of a typical filterelement over a period of time. It can be seen that the effectiveness ofa typical filter element decreases with time until it becomes necessaryto clean or replace the filter element.

[0034] Referring back to FIG. 1, in order to control the accumulation ofcatalyst fines in the reactor slurry, reactor system 100 includesseparation system 220. Reactor slurry enters settling chamber 280 fromreactor 110 via line 235. Settling chamber 280 is arranged so that thereactor slurry will move through chamber 280 with a velocity such thatsolid catalyst particles having at least a predetermined size willsettle towards the bottom of the chamber and be recycled into reactorchamber 120 via line 230. Particles smaller than the predetermined sizewill remain suspended. Outlet line 210 is provided to draw off asub-particle rich stream and is specifically sized, placed, and operatedso as to remove a minimum amount of catalyst particles having at leastthe predetermined size. Therefore, the sub-particle rich stream that isdrawn off through outlet 210 will preferably only contain those catalystsub-particles (fines) that are detrimental to the system. The flow rateof the sub-particle rich stream through outlet 210 and the slurry levelin the settling chamber 280 can each be controlled so as to continuouslyor intermittently remove catalyst fines from the reactor slurry, therebyreducing or maintaining the overall quantity of catalyst fines in thereactor system. The sub-particle rich stream through outlet 210 can befurther processed continuously or intermittently to recover liquidproducts.

[0035] Thus, the presence of catalyst fines in the reactor slurry can becontrolled by using settling system 220 to continuously orintermittently remove the undesirable particles from the system. Theparticle size distribution within the reactor slurry can then bemaintained within a desired range in order to improve the effectivenessof the catalyst-liquid separation, in particular filtration. Because thepresent system prevents the catalyst particle size distribution fromdeteriorating significantly over time, the catalyst-liquid separationsystem does not have to be designed to accommodate the eventualaccumulation of catalyst fines. This enables the use of more effectivefiltration systems. FIG. 4 illustrates the improvement in filterefficiency wherein the dotted line illustrates the efficiency of atypical filtration system over time and the solid line corresponds to animproved efficiency of a filtration system constructed in accordancewith the preferred embodiments, in which most of the catalyst fines areselectively removed from the system.

[0036] Settling system 220 helps to remove catalyst fines by takingadvantage of the density difference between the solid catalyst and theliquid hydrocarbons. Settling system 220 is preferably a gravitationalsedimentation system but may also be a centrifuge, a hydrocyclone, orsome other device that seeks to take advantage of the densitydifferences between the catalyst and the hydrocarbons. The settling ofsingle particles can be described using a combination of Newton's law,which relates to the forces acting on the particle, and Stokes' law,which takes into account the drag forces on the particle as it movesthrough the fluid. The time (t) that it takes for a particle to travel adistance (L) is given by:

t=(18/G)(μ/ρ)(L/D ²)  (1)

[0037] where t is the fall time (sec), ρ is the particle density(g/cm³), μ is the viscosity of the liquid (g/cm-sec), L is the falldistance (cm), D is the particle diameter (cm), and G is the effectiveacceleration (cm/sec²) given by: $\begin{matrix}{G = {{g\left( {1 - \frac{\rho_{f}}{\rho}} \right)}N}} & (2)\end{matrix}$

[0038] where g is the acceleration due to gravity (980 cm/sec²), ρƒ isthe fluid density (g/cm³), and N is the number of g's.

[0039] As can be seen in Equation 1, the time (t) that it takes for aparticle to settle a given distance is dependent on its diameter. Thelarger the diameter of the particle, the faster the particle willsettle. Therefore, the difference in settling velocity of particles withdifferent diameters can be used to segregate the particles according totheir size.

[0040] Referring now to FIG. 5, one embodiment of settling system 220 isshown. Settling system 220 includes a settling chamber 280 that hasinlet line 235 and outlet lines 210, 230, and 240. Suspended in thereactor slurry as it enters settling chamber 280 are catalyst particles430 and catalyst sub-particles 420. Settling chamber 280 is sized so asto control the velocity of the reactor slurry as it moves through thechamber. The flow through outlet 210 is preferably controlled so as toencourage sedimentation of catalyst particles.

[0041] As the reactor slurry enters chamber 280, catalyst particles 420and 430 will move towards lower portion 450 of the chamber at differentsettling velocities. As shown by Equation 1, particles 430 will have ahigher settling velocity than sub-particles 420. Outlet 210 ispreferably located near upper portion 460 of chamber 280 and draws asub-particle rich stream from the chamber Outlet 210 preferably drawsthe sub-particle rich stream with a controlled flow so that the overflowvelocity of the liquids is lower than the settling velocity of particles430 but higher than the settling velocity of sub-particles 420.

[0042] Therefore, chamber 280 and outlet 210 can be designed so thatprimarily the catalyst fines having a certain size are removed throughthe outlet via the sub-particle rich stream. Outlet 210 may actuallycomprise several individual outlets as may be required to meet theseparation requirements of the reactor. A plate, or other vesselinternal structure, may be used to improve the performance of settler220. A portion of the liquid products can therefore be recovered vialine 210 after further processing to remove the fines 420.

[0043] Referring back to FIG. 1, for the purpose of discussion only, andby way of an example, the operation of reactor system 100 will bedescribed as a Fischer-Tropsch reactor system. Syngas, containinghydrogen and carbon monoxide, is fed through inlet line 115 into reactorchamber 120, which contains catalyst particles 180 suspended in aslurry. As the syngas bubbles travel through the reactor slurry, thereactants (hydrogen and carbon monoxide) are absorbed into the liquidhydrocarbons present in the slurry and diffuse to the catalyst wherethey are converted to gaseous and liquid products. The gas products areremoved from reactor 120 through line 125 while liquid products mix withthe reactor slurry.

[0044] Preferably located near the top of the reactor chamber 120, lines235 and 260 draw off reactor slurry from the reactor into settlingsystem 220 and catalyst-liquid separation system 250, respectively.Settling and separation systems 220 and 250 may be gravity fed and relyon the density difference between the slurry inside the reactor, whichis mixed with gas, and the slurry outside the reactor, which issubstantially gas-free. Although systems 220 and 250 are depicted asforming separate, distinct flow loops through which the slurry iscirculated, they may also operate on a single flow loop, as shown inFIG. 6 and discussed in detail below. It should be understood that morethan one settling system 220 and/or more than one catalyst-liquidseparation system 250, either arranged in series, parallel or suitablecombinations, may be used.

[0045] Referring again to FIG. 1, in settling system 220, slurry enterssettling chamber 280 through line 235. Outlet 210 acts, as describedabove, to draw off a sub-particle rich stream while minimizing the lossof catalyst particles above a predetermined size. The remainingsub-particle lean stream, which contains particles of catalyst 180having at least a predetermined size, exits chamber 280 and is recycledinto reactor 110 via line 230. The sub-particle rich stream that iswithdrawn through outlet 210 is preferably further processed to separatethe sub-particle from the liquid products. Settling system 220 mayoperate continuously or intermittently as required to maintain theaccumulation of catalyst fines in the slurry within desired limits.

[0046] In catalyst-liquid separation system 250, reactor slurry entersseparation unit 290 via line 260. Separation unit 290 removes catalyst180 from the slurry and produces a catalyst-lean stream through outlet205. A catalyst-rich stream is recycled to reactor 110 via line 270while the output of the catalyst-lean stream through outlet 205 providesmost of the products that are liquid at operating temperature andpressure of reactor system 100. Separation unit 290 may use filtration,gravitational separation, magnetic separation, or any other method toproduce a relatively clean liquid product. One such filtration system isdiscussed in Provisional Patent Application No. 60/372,961, titled“Solid/Liquid Separation System for Multiphase Converters,” which ishereby incorporated by reference herein for all purposes.

[0047] Referring now to FIG. 6, an alternative embodiment of a slurrybubble column reactor system 500 is shown. Reactor system 500 includesreactor 510 and a single circulation loop that includes both a settlingsystem 620 and a catalyst-liquid separation system 650. As in FIG. 1,reactor 510 includes a reactor chamber 520 containing a catalystsuspended in a slurry. Gas inlet line 540 provides feed gas to reactor510 while gas outlet 560 removes gases from the reactor. Settling system620 includes line 630 providing reactor slurry from reactor 510 tosettling chamber 680. Settling system 620 also includes a first outlet700 for a sub-particle rich stream that removes material from system500, a gas outlet 665, and a second outlet line 720. Optionally, adegasser vessel (not shown) may remove gas from the slurry before itenters chamber 680. Gas outlet 560 from reactor 510 and gas outlet 665from settling system 620 can be combined into one single gas outlet, asshown in FIG. 6, but it should be understood that they do notnecessarily need to be combined. It is also understood that any gasoutlet from any optional degasser also could be combined or not with anyof the two gas outlets 560 and 665.

[0048] Catalyst-liquid separation system 650 draws reactor slurry fromoutlet line 720 into separation unit 760, which outputs a catalyst-leanstream through a first outlet 780 and recycles a catalyst-rich streaminto reactor chamber 520 through second outlet line 800. Alternatively,the location of catalyst-liquid separation system 650 and settlingsystem 620 can be reversed such that settling system 620 is downstreamof catalyst-liquid separation system 650. Settling system 620 may alsooptionally include an internal plate 525, or other internal structure,for improving the settlement characteristics of chamber 680.

[0049] Although the removal of catalyst fines from the slurry providesdesirable benefits to catalyst-liquid separation that uses filtration,other catalyst-liquid separation mechanisms may also be aided by thecontrol of fines, increasing the overall efficiency of the liquid-solidsseparation system. Some of the other separation techniques that willbenefit are magnetic-based techniques, gravitational-based techniques,such as centrifugation, settling, or hydrocyclone solubility-basedtechniques, and coagulation.

[0050] The embodiments set forth herein are merely illustrative and donot limit the scope of the invention or the details therein. It will beappreciated that many other modifications and improvements to thedisclosure herein may be made without departing from the scope of theinvention or the inventive concepts herein disclosed. Because manyvarying and different embodiments may be made within the scope of thepresent inventive concept, including equivalent structures or materialshereafter thought of, and because many modifications may be made in theembodiments herein detailed in accordance with the descriptiverequirements of the law, it is to be understood that the details hereinare to be interpreted as illustrative and not in a limiting sense.

What is claimed is:
 1. A slurry bubble column reactor system comprising:a reactor containing solid catalyst particles and liquid productssuspended in a slurry; a first separation unit adapted to produce asub-particle rich stream comprising at least a portion of the catalystparticles having a size below a predetermined limit from the slurry; anda second separation unit adapted to produce a catalyst-lean streamcomprising at least a portion of the liquid products from the slurry,wherein the sub-particle rich stream and the catalyst-lean stream areremoved from the reactor system.
 2. The system of claim 1 wherein saidfirst separation unit is adapted to produce a sub-particle lean streamthat is recycled into said reactor.
 3. The system of claim 1 whereinsaid first separation unit is adapted to produce a sub-particle leanstream that feeds said second separation unit.
 4. The system of claim 1wherein said second separation unit is adapted to produce acatalyst-rich stream that is recycled into said reactor.
 5. The systemof claim 1 wherein said second separation unit is adapted to produce acatalyst-rich stream that feeds the first separation system.
 6. Thesystem of claim 1 wherein said first separation unit comprises asettling system.
 7. The system of claim 6 wherein the settling systemutilizes gravitational settling.
 8. The system of claim 1 wherein thesecond separation unit comprises a catalyst-liquid separation system. 9.The system of claim 8 wherein the catalyst-liquid separation systemcomprises a filtration system.
 10. The system of claim 1 wherein thesub-particle rich stream further comprises at least a portion of theliquid product.
 11. A slurry bubble column reactor system comprising: areactor containing solid catalyst particles, including sub-particles,and liquid products suspended in a slurry; a first flow loop thatremoves a sub-particle rich stream from the system; and a second flowloop that removes a catalyst-lean stream from the system.
 12. The systemof claim 11 wherein said first flow loop further comprises a settlingsystem that utilizes gravitational forces to produce the sub-particlerich stream.
 13. The system of claim 11 wherein said sub-particle richstream further comprises at least a portion of the liquid products,further including means for recovering liquid products from saidsub-particle rich stream.
 14. The system of claim 11 wherein said secondflow loop further comprises a catalyst-liquid separation system adaptedto produce the catalyst-lean stream.
 15. The system of claim 14 whereinsaid catalyst-liquid separation system comprises a filtration system.16. A slurry bubble column reactor system comprising: a reactorcontaining solid catalyst particles and liquid products suspended in aslurry; a first outlet that removes from the reactor a sub-particle richstream; and a second outlet that removes from the reactor acatalyst-lean stream.
 17. The system of claim 16 further comprising afirst flow loop connected to said first outlet.
 18. The system of claim17 wherein said first flow loop further comprises a settling system thatutilizes gravitational forces to remove the sub-particle rich stream.19. The system of claim 16 further comprising a second flow loopconnected to said second outlet.
 20. The system of claim 19 wherein saidsecond flow loop further comprises a catalyst-liquid separation systemadapted to produce the catalyst-lean stream.
 21. The system of claim 20wherein said catalyst-liquid separation system comprises a filtrationsystem.
 22. The system of claim 16 wherein said sub-particle rich streamincludes at least a portion of the liquid products.
 23. A method forseparating catalyst particles from liquid products in a slurry in areactor, comprising: removing from the reactor a sub-particle richstream; and removing from the reactor a catalyst-lean stream.
 24. Themethod of claim 23 wherein the sub-particle rich stream is removed in afirst flow loop comprising a settling system that utilizes gravitationalforces.
 25. The method of claim 23 wherein the catalyst-lean stream isremoved in a second flow loop comprising a catalyst-liquid separationsystem.
 26. The reactor of claim 25 wherein said catalyst-liquidseparation system comprises a filtration system.
 27. The system of claim23 wherein said sub-particle rich stream comprises at least a portion ofthe liquid products, further including means for recovering liquidproducts from said sub-particle rich stream.
 28. A slurry bubble columnreactor comprising: solid catalyst particles and liquid productssuspended in a slurry; a first separation device that divides at least aportion of the slurry into a sub-particle rich stream and a sub-particlelean stream; a first outlet from said first separation device thatremoves the sub-particle rich stream from the reactor; and a secondseparation device adapted to divide the sub-particle lean stream into acatalyst-rich stream and a catalyst-lean stream.
 29. The reactor ofclaim 28 wherein said first separation device further comprises asettling system that utilizes gravitational forces to divide the slurry.30. The reactor of claim 28 wherein said second separation devicecomprises a filtration system.
 31. The system of claim 28 wherein saidsub-particle rich stream includes at least a portion of the liquidproducts.